Mary Alexander thought it was a great idea when she agreed to sell her flat in Stirling, Scotland and come to live with her sister, Rhona, in sunny Southsea.

Before she put the harsh Scottish winters behind her, the 78-year-old widow and former nurse meticulously went about organising the move, including closing her gas and electricity account with Scottish Power in September, 2014.

But more than two years after the account was settled, she was astounded when bills started turning up at her shared home claiming she still owed a mammoth £1,842.63.

Last October, Rhona, 84, helped Mary compose a stiff letter of complaint to the energy giant insisting the claim was preposterous.

The confused couple asked the firm to look into the matter urgently and to stop sending further bills and demands for payment.

Mary says: ‘I just couldn’t understand it. The first I knew of the mysterious debt was when the first bill arrived threatening to blow a massive hole in my savings.

‘In only a few weeks it became obvious no-one at Scottish Power was listening. They sent me another letter and bills for different amounts insisting on immediate payment.

‘I was so furious I tried to phone them at least half-a-dozen times about it, but on each occasion I was kept waiting to speak to their customer services for almost half-an-hour.

‘When I finally got through to someone, they said they’d look into it straight away and ring me back, but that always turned out to be a worthless empty promise. All I seemed to be doing was trying to explain, but there were no answers and no let-up in demands for payment.

‘Like Rhona, I rarely get uptight about anything, but the entire experience left me sick with worry and frustration.

‘I got the solicitor who handled the conveyancing of my flat to confirm it had been sold two years earlier and the date I moved out. I then wrote to Scottish Power’s managing director enclosing a copy of the letter, but it wasn’t even acknowledged.

‘The whole thing was completely nonsensical. They’d obviously got me confused with someone who, in the meantime, must have been using the gas and electric and hadn’t settled their bill.

‘I said the matter was so outrageous and obviously wrong I was just going to ignore any further demands for payment come what may.’

Despite believing her strident ultimatum to the firm’s senior management would be an end to the matter, she was mistaken.

The row was to move up a further notch when the only response was a letter from Scottish Power’s recovery team claiming Mary owed them £812.27 for electricity and £1,030.36 for gas.

Within weeks she found herself being robustly chased by debt collectors, who accused her of repeatedly ignoring a number of letters from Scottish Power after she’d moved out.

If she didn’t pay up promptly, they’d start court proceedings and costs which would increase the sum she owed.

At her wits’ end and not knowing where to turn for help, Rhona suggested they phone Citizens’ Advice about the situation.

Subsequently an adviser wrote to the company explaining in detail Mary’s plight, asking them to justify their relentless attempt to bill her for energy she couldn’t possibly have used.

But the letter was ignored and to her dismay a further bill arrived, this time supposedly for energy consumed when she actually lived in the flat.

A furious Mary was considering what to do next when a neighbour suggested it might be a good idea to contact Streetwise to see if we could get the problem sorted.

Her experience has been reflected in a number of News reader complaints about Scottish Power, who were fined by the regulator Ofgem a record £18m in 2016 for shoddy service, inadequate call handling and billing.

We got on to the provider about Mary’s predicament and to their credit they quickly sorted things out.

A spokesperson said: ‘We were very sorry to learn of the difficulty Mrs Alexander experienced when she got in touch with customer services about the account.

‘We confirm the account was finalised in September, 2014 when she informed us she was moving out.

‘It was discovered during a routine check of accounts in 2016 that gas and electricity was being used at the property, but we had no record of anyone registering the supply.

‘We erroneously billed the supply to Mrs Alexander, which explains why she was sent further demands for payment.

‘We have spoken to her about the misunderstanding and to apologise for her distress we have agreed to send her a cheque for £100 as a gesture of goodwill.’

Mary was both astounded and delighted that we had resolved her battle with the firm and achieved a positive result.

She says: ‘You managed to get fixed for me within a few days what we’d been wrestling with for almost six months.

‘I honestly don’t know what I’d have done without your help.

‘I really can’t thank you enough for the way you brought my dreadful experience with this company to an unexpected but very satisfactory conclusion.’